An air refrigerant cooling/heating system is composed of an air refrigerant type cooling apparatus, a heat exchanger, and a cooling chamber, and an object thereof is to sustain products which are stored in the cooling chamber and required to be frozen to be at low temperatures.
In a freezing device used in a conventional cooling/heating system, a stator portion of a motor is water-cooled (or oil-cooled) in order to cool down the driving motor. Alternatively, as shown in an air cooling motor 1 in FIG. 1, an external fin 5 is connected to the outside of a stator casing 6, and the air cooling motor 1 is air-cooled as a whole by an air cooling fan 2 installed in the main shaft 7 via the external fin 5.
In the conventional air cooling motor 1, a stator is a main heat generating portion, and in comparison with a stator coil main body 4 and a stator coil end portion 3 which are configuration requirements of the stator, the stator coil main body 4 has a higher heating ratio. Therefore, the stator coil main body 4 is connected to the stator casing 6, and the external fin 5 connected to the outside of the stator casing 6 is simply cooled down by the air cooling fan 2 so that cooling the motor as a whole is achieved.
However, there is a demand in recent years to enhance efficiency of the air refrigerant cooling/heating system and store products at much lower temperatures. In order to meet the demand, it is necessary to enhance efficiency and improve reliability of the air refrigerant type cooling apparatus, in addition to increase performance thereof.
For efficiency improvement in the air refrigerant type cooling apparatus, it is considered to increase a rotation speed of the motor, and in order to sustain the high speed rotation, it is necessary to enhance heat exhausting efficiency in the inside of the motor for reliability enhancement and improve reliability in a supporting mechanism of the main shaft being a rotational driving portion of the motor.
However, if the motor is controlled by using a general-purpose inverter panel while rotating the motor at a high speed, the frequency of the inverter needs to be lowered by reducing the number of poles of the motor. If the pole number of the motor is reduced, a ratio of the length in the stator coil end portion is increased to the length of the stator main body in the configuration of the motor. If the ratio of the length in the stator coil end portion is increased, a heating value from the stator coil end portion is increased at the time of driving the motor, so that it is insufficient in the conventional motor cooling method to cool down the motor as a whole.
In relation to the technique described above, there are proposals as follows.
An air cooling motor disclosed in Japanese Laid Open Patent Application (JP-P 2003-158839A) includes a plurality of cooling holes provided along the shaft direction of a stator core composed of a laminated core, a motor shaft to which a rotor core to be composed of a laminated core and provided via a magnetic air gap from the stator core is bonded in the outer periphery, a load-side bracket for supporting a front end portion of the stator core by protruding a front end portion of the motor shaft, an anti-load-side bracket for supporting a rear end portion of the stator core by protruding a rear end portion of the motor shaft, a housing provided in the outer periphery of the anti-load-side bracket via a space so as to seal the rear end portion of the stator core, and a fan unit having a forced air cooling fan in the rear of the housing. In the air cooling motor configured to cause cooling air to flow from the cooling holes toward the space surrounded by the housing and the load-side bracket, the load-side bracket and the anti-load-side bracket have a plurality of cooling holes, and have a guide which is arranged to guide cooling air introduced from the cooling holes of the load-side bracket to the motor shaft, and to cover coils provided in the stator core, so that proposed there is the air cooling motor provided with a plurality of through holes in the motor shaft to allow cooling air introduced from the cooling holes of the load-side bracket to flow toward the cooling holes of the anti-load-side bracket.
Moreover, in relation to the air refrigerant cooling/heating system using an air refrigerant type freezing device, an air refrigerant type freezing device disclosed in Japanese Laid Open Patent Application (JP-A-Heisei, 11-132582) includes a compressor, an air cooler, an air-to-air heat exchanger, and an expander to be disposed in an air passage in the order of air flow, in which air in a chamber required to be cooled is introduced to the compressor via the air-to-air heat exchanger, and air from the expander is blown into the chamber required to be cooled. The air refrigerant type freezing device to be proposed is further provided with a interposal first bypass for returning the air from the expander partially or entirely back to the air-to-air heat exchanger while bypassing the chamber required to be cooled, and an interposal hot air bypath for introducing air of 0° C. or above from the air passage between the compressor and the expander and providing the air for the air passage in the inlet side of the air-to-air heat exchanger.